On the Mechanism of Theta Capillary Nanoelectrospray Ionization for the Formation of Highly Charged Protein Ions Directly from Native Solutions.

Theta capillary nanoelectrospray ionization (θ-nanoESI) can be used to "supercharge" protein ions directly from solution for detection by mass spectrometry (MS). In native top-down MS, the extent of protein charging is low. Given that ions with more charge fragment more readily, increasing charge can enhance the extent of sequence information obtained by top-down MS. For θ-nanoESI, dual-channeled nanoESI emitters are used to mix two solutions in low to sub-µs prior to MS. The mechanism for θ-nanoESI mixing has been reported to primarily occur: (i) in a single shared Taylor cone and in the droplets formed from the Taylor cone or (ii) by the fusion of droplets formed from two separate Taylor cones. Using θ-nanoESI-ion mobility MS, native protein solutions were rapidly mixed with denaturing supercharging solutions to form protein ions in significantly higher charge states and with more elongated structures than those formed by premixing the solutions prior to nanoESI-MS. If θ-nanoESI mixing occurred in the Taylor cone and in the droplets resulting from the single Taylor cone, then the extent of protein charging and unfolding should be comparable to or less than that obtained by premixing solutions. Thus, these data are consistent with mixing occurring via droplet fusion rather than in the Taylor cone prior to ESI droplet formation. These data also suggest that highly charged protein ions can be formed by the near-complete mixing of each solution. The presence of supercharging additives in premixed solutions can suppress volatile electrolyte evaporation, limiting the extent of protein charging compared to when the additive is delivered via one channel of a θ-nanoESI emitter. In θ-nanoESI, the formation of two Taylor cones can presumably result in substantial electrolyte evaporation from the ESI droplets containing native-like proteins prior to droplet fusion, thereby enhancing ion charging.

The clinical presentation and magnetic resonance imaging characteristics of an infant with idiopathic orbital inflammation.

Idiopathic orbital inflammation is rare in the pediatric population, particularly infants. It can be mistaken either for orbital infection or malignant tumors. We report the case of a 9-month-old previously healthy white boy who presented with right upper eyelid swelling. Magnetic resonance imaging revealed an abnormal T2-hypointense enhancing lesion within the extraconal superior right orbit.

Operationalizing the 2018 World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) Cancer Prevention Recommendations: A Standardized Scoring System.

BACKGROUND: Following the publication of the 2018 World Cancer Research Fund (WCRF) and American Institute for Cancer Research (AICR) Third Expert Report, a collaborative group was formed to develop a standardized scoring system and provide guidance for research applications. METHODS: The 2018 WCRF/AICR Cancer Prevention Recommendations, goals, and statements of advice were examined to define components of the new Score. Cut-points for scoring were based on quantitative guidance in the 2018 Recommendations and other guidelines, past research that operationalized 2007 WCRF/AICR Recommendations, and advice from the Continuous Update Project Expert Panel. RESULTS: Eight of the ten 2018 WCRF/AICR Recommendations concerning weight, physical activity, diet, and breastfeeding (optional), were selected for inclusion. Each component is worth one point: 1, 0.5, and 0 points for fully, partially, and not meeting each recommendation, respectively (Score: 0 to 7-8 points). Two recommendations on dietary supplement use and for cancer survivors are not included due to operational redundancy. Additional guidance stresses the importance of accounting for other risk factors (e.g., smoking) in relevant models. CONCLUSIONS: The proposed 2018 WCRF/AICR Score is a practical tool for researchers to examine how adherence to the 2018 WCRF/AICR Recommendations relates to cancer risk and mortality in various adult populations.

Supercharging protein ions in native mass spectrometry using theta capillary nanoelectrospray ionization mass spectrometry and cyclic alkylcarbonates.

Theta nanoelectrospray ionization of protein ions formed from aqueous buffer solutions that are mixed with denaturing solutions containing cyclic alkylcarbonates (e.g., vinyl ethylene carbonate; VEC) results in a significant increase in the extent of ion charging compared to native mass spectrometry. For six proteins, the extent of ion charging can be significantly higher than that obtained using denaturing solutions and alternative native "supercharging" methods. In theta nanoelectrospray supercharging, the extent of charging scales with protein mass in agreement with an analytical scaling relationship for ions with elongated structures. Theta nanoelectrospray supercharging of non-covalent complexes from native solutions results in essentially the complete loss of protein-ligand and protein-protein interactions. Based on circular dichroism spectroscopy, VEC can effectively denature proteins in buffered solutions. These data provide evidence that enrichment of VEC in theta nanoelectrospray ionization generated droplets can denature proteins on the timescale of droplet desolvation and ion formation. This approach can be used to form highly charged protein ions from native solutions containing biological buffers, including some that are considered incompatible with native MS. Forming some protein ions in the highest reported charge states directly from native solutions is no longer a challenge in obtaining primary structural information using tandem mass spectrometry.

2D IR spectroscopy at 100 kHz utilizing a Mid-IR OPCPA laser source.

We present a 100 kHz 2D IR spectrometer. The system utilizes a ytterbium all normal dispersion fiber oscillator as a common source for the pump and seed beams of a MgO:PPLN OPCPA. The 1030 nm OPCPA pump is generated by amplification of the oscillator in cryocooled Yb:YAG amplifiers, while the 1.68 µm seed is generated in a OPO pumped by the oscillator. The OPCPA outputs are used in a ZGP DFG stage to generate 4.65 µm pulses. A mid-IR pulse shaper delivers pulse pairs to a 2D IR spectrometer allowing for data collection at 100 kHz.

Bright coherent ultrahigh harmonics in the keV x-ray regime from mid-infrared femtosecond lasers.

High-harmonic generation (HHG) traditionally combines ~100 near-infrared laser photons to generate bright, phase-matched, extreme ultraviolet beams when the emission from many atoms adds constructively. Here, we show that by guiding a mid-infrared femtosecond laser in a high-pressure gas, ultrahigh harmonics can be generated, up to orders greater than 5000, that emerge as a bright supercontinuum that spans the entire electromagnetic spectrum from the ultraviolet to more than 1.6 kilo-electron volts, allowing, in principle, the generation of pulses as short as 2.5 attoseconds. The multiatmosphere gas pressures required for bright, phase-matched emission also support laser beam self-confinement, further enhancing the x-ray yield. Finally, the x-ray beam exhibits high spatial coherence, even though at high gas density the recolliding electrons responsible for HHG encounter other atoms during the emission process.